The present invention relates to detection of corrosion of cathodically protected, CP, buried pipelines by use of probes buried in the soil adjacent to the pipelines and electrically connected to the pipelines. More specific, the invention relates to detection of corrosion caused by the combined effect of specific soil parameters and electric fields such as DC stray current or AC voltage induced as a result of paralleling the pipeline with high voltage power lines. Such corrosion is sometimes found to proceed although measures have been taken to eliminate the corrosion effects, e.g. by imposing DC current to the pipeline by an external electrode and a rectifier system, or by sacrificial anodes coupled to the pipe. Usual acceptance criteria (safe/not safe with regard to corrosion) are built upon the DC potential of the pipeline, but specifically in the case of AC induced corrosion, these criteria are not reliable.
Related apparatuses and techniques are described in publications such as US 2003/006148, GB 2 064 124, EP 0 882 975, EP 0 560 443 and EP 1 152 235. Preference is made to all of the above mentioned patent publications and all are hereby incorporated the present specification by reference.